Nervous System Flashcards
Describe development of notochord.
The primitive node provides cells that form notochord. The cellular precursors migrate forward and left behind has rodlike aggregation as primitive streak regresses. Notochord also cells fuse with endodermis cells and form a temporary neurenteric canal. Notochordal cells separate from endoderm and form solid notochord.
What is the relationship of Nodal to the establishment of the anteroposterior axis and what is the role of Lefty 1 and Cer1?
Lefty 1 and Cer1 block nodal to set up a gradient. Lefty and Cer1 are towards the cranial end and will have low levels of nodal while the posterior end has high levels.
How is Wnt3 related to Nodal?
Wnt3 is at the posterior end of the epiblast and signals Nodal to be activated.
What signaling molecules are involved in inhibition of posterior structure?
Cerberus-Like inhibits posterior structures and is from the anterior visceral endoderm.
DKK-1 also inhibits development of posterior structures and originates from anterior visceral endoderm and blocks Wnt.
What signaling molecule from primitive node are involved in neural induction?
Noggin and Chordin both induce neural and are from primitive node.
Nodal is a signaling molecule produced by primitive node what is it s role in the induction of primitive streak and left right symmetry?
Nodal induces the primitive streak…..
What is the source land role of signaling molecules Cerberus-like and DKK-1 in the development of anteriorposterior axis?
They come from Anterior visceral endoderm and they inhibit development of posterior structures.
What are the origin and effects of TF’s Goosecoid and Brachyury in regard to early primitive streak?
Goosecoid originates from primitive node and it activates Chordin and nogggin.
Brachcyury originates from the primitive streak and it effects notochord formation and allows for normal movements of cells through primitive streak.
What genes are targeted by Goosecoid?
Chordin and Noggin
What are the effects of Foxa-2 on early primitive streaks?
Establishment of primitive node and initiates notochord function. Also established midline structures cranial to node.
What are classical markers of organizer region in vertebrates?
Chord in, Goosecoid, and Fox-2
In late primitive streak what signaling molecule induces axial structures?
Sonic Hedgehog
In late primitive streak what signaling molecule is necessary for head formation?
Cerberus-1
In late primitive streak stage what signaling molecules are needed for neural induction and what is their origin?
Noggin Chordin and Shh they are all from the notochord.
In late primitive streak stage what signaling molecules are released from primitive streak activate Hox genes?
RA, Wnt, FGF
Describe experiments on amphibian and higher. Vertebrates that led to understanding of neural induction.
The dorsal lip of the blastopore is the organizer. The took dorsal lip from a donor blastocyst and transferred it into the blastocoele and it now has two blastopores. The result is two separate embryos.
Took section of hensen’s node prone primitive streak and placed it into a donor. The embryo resulted in host embryo and an induced neural tube.
Difference between determination and differentiation
Determination is when cells or part of embryo becomes restricted to a certain dev path, it becomes committed to a cell line.
Differentiation is a set of changes involved in the specialization of structure and function, results in luxury molecules.
What is the first sign of asymmetry in early development? Role of Nodal and Lefty?
Fist sign involves the beating of cilia around the primitive node. Asymmetrical beating results in a directional current and expression of TGF-Beta.
Nodal is symmetry breaking molecule in the left side of the embryo.
Lefty-1 is on the left side of the primitive streak.
Describe the distribution of CAM’s in early ectoderm.
E Cadherins are found in the preinduced ectoderm along with N-CAM.
The ectoderm then evolves to just become E cadherins.
The neural tube will have N-CAM’s and N- cadherins.
List stages of neural tube development.
- Formation of thickened neural plate
- Shaping of neural plate
- Folding of neural plate
- Formation of neural tube
Explain process of convergent extension.
Involves migration of ectodermal cells to the midline. Ectodermal cells elongate along the anterior-posterior axis and become thinner forming elongated narrow plate.
What role does planar polarity play in formation of neural plate?
It causes cells to become oriented along an axis in a flat plane. It is caused by asymmetric distribution of planar cell polarity proteins Dishevelled and Prickle.
The PCP convert elliptical gastrula into keyhole shaped neurula and are important in folding of plate into the tube.
Describe significance of median and lateral hinge points in neural tube formation.
Median hinge point is induced by notochord and involves changing columnar cells shape to pyramidal shaped cells and apical constriction.
Lateral hinge points involve apical constriction by actin filaments.
What roles do Oxt-2, Gbx-2 Wnt-8, Shh, FGF-8 play in the segmentation of spinal cord?
Otx-2: expressed in forebrain/midbrain,, Isthmmic organizer is established by boundary between Otx-2 and God-2 and Releases Wnt-1 and FGF-8.
Gbx-2: Expressed in hindbrain region
Wnt-8: establishes anterior posterior gradient
Shh: Secreted by anterior neural ridge signaling center important for organizing telencephalon, diencephalon olfactory area and pituitary gland.
FGF-8: released posteriorly from the isthmic organizer also secreted from anterior neural ridge signaling center (same function as Shh)
RA:
